When counseling persons caught up in addiction to drugs and other substances, it is often important to remind them that addiction is forever; that is, despite denial, wishful thinking, and the most fervent prayer, it (the problem) is not going away.

I'm looking for the Irish that most accurately captures that semtiment. Here's what I've come up with:

Ní bhíonn sé ag dul ar shiúl.
Ní théann sé ar shiúl.
Ní rachaidh sé ar shiúl.
Níl sé ag imeacht.

Any of these seem to hit the mark?

Not really; they all convey the sense of something concrete physically moving; it doesn't feel right.

"Ní rachaidh sé ar shiúl."

is probably the best of them.

Sometimes it's better to invert:

"Beidh sé leat i gcónaí"

Or

Ní gheobhaidh tú réidh leis ar fad riamh